Desk and interpolator combination



' Oct. 15, 1963 G. A. MoALls-l-ER, JR 3,106,789

DESK AND INTERPOLATOR COMBINATION Filed March 27, `1961 lA u ossl l2 o 54 0599 aan as :s nag n oa was |27: l I4 xg :4 gaa |553 r 4 l :g 5.a. Mg Lfz'al ).221 1? |11 2304 ao 23252 o a sI -ess-aa 218s m f as 2 Pa 0 l 3 solo a ,w54 sms 9s al 3222 324s sass 3284 a 3f 5424 44| 3464 ansa' s o2' S .J I c|7 :l 2c :A55 357 24. 5802 3 o 74 3 o l 2 4 Angle Lsin d Heos d Lfd", i .3`1z; @.2333 0 as. .4 7 32g' 7.7i 3o. 3^ o o 15721 7.90 |20 0.00 o 9 |249 40' 8.06 9 0 0 .06 959 8.462 72 l 27 '792 l 0 4| 9 o o 9.39% 3 8 f5 INVENTOR I .44 a .9 Arm 57| sos l .4558' 8 0 g g- 3 5 George A McAllster, Jr.

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lo 1 .9997 t? 9 22 j ""ZZ- zu. 9.9996 o o n I ,o 9:9996I u .s 25,. f BY 5 ,7 ,7 ATTORNEY United States Patent O 3,106,79 DESK AND INTERILATOR COMBINATION George A. McAlister, Jr., Big Spring, Tex., assigner to Math-Master Labs, Incorporated, Big Spring, Tex., a corporation of Texas Filed Mar. 27, 1961, Ser. No. 98,493 1 Claim. (Cl. 35-60) This invention is concerned with an interpolator device, and is particularly concerned with a desk, having logarithmic and trigonometric tables on the top thereof, which is used in conjunction with a special transparent arm slidable over the top of the forms with vertical and horizontal indicator lines thereon to bracket adjacent vertical and laterally arranged logarithm numbers to permit ease. convenience and speed in interpolation between bracketed numbers. A special T-head is provided on the arm having a magnetic inner surface thereon slidable along the edge of the table, and attracted thereto, to disengageably and slidably attach the arm in a desired position to maintain the bracketed numerals for interpolation.

The apparatus described and claimed herein is primarily intended for use in the classroom as a teachers aid in teaching mathematics, but it will be understood that it can be employed in architects and engineers ofces for ease and quickness in interpolation between numerals on logarithm or other mathematical tables.

Logarithmic and trigonometric forms are customarily printed in the back of a math text book or in a separate book, so that to use them it is necessary for the user to divert his attention from the problem and its location in the text. Also, no means has been heretofore shown for providing convenient means for bracketing adjacent logarithmic and trigonometric iigures for interpolation. As a result the student or other person making the interpolation must hold his finger or fingers of one hand on the numerals to be interpolated between, while he performs the computation with the other hand. In glancing back and forth between the logarithmic table and the work sheet, he often loses the proper place in the logarithmic table and adds the interpolated amount to the wrong tabular value, thereby introducing an unnecessary error into the solution to the problem.

The device disclosed and claimed herein provides a convenient desk having a slanted top with logarithmic and trigonometric tables overlaid thereon with a transparent rule or arm slidable over the top of the table, with spaced parallel horizontal lines on the arm to bracket adjacent lateral and vertical tabular values therebetween. A laterally slidable cursor of transparent material is provided on the arm, having vertical, spaced, parallel lines thereon, for bracketing a column of figures to be interpolated. The arm may be retained in any desired position on the table, by a magnetic T-head slidable along the metallic border of the table, so that the tabular values to be, interpolated between, can be bracketed vertically and horizontally, and the student or other person Working with the device will have both hands free for working, and can be assured when reference is made between his work sheet and the tabular values that an error will not be made by interpolation between the wrong tabular values, or from adding an interpolated value to the wrong tabular value.

It is, therefore, a primary object of the invention to provide an interpolator device wherein the chance of error is reduced to a minimum.

Another object of the invention is to providean interpolator device, wherein the interpolation between adjacent tabular values may be made quickly, easily and accurately.

Still another object of the invention is to provide an interpolator device wherein tabular values may be brack- Patented Oct. i5, 1963 ICC eted vertically and horizontally, and maintained in bracketed position to give the user freedom of use of both hands, and may be permitted to leave his work and return thereto with the assurance that the correct bracketed tabular values will remain ina xed position.

A still further object of the invention is to provide a desk with mathematical formula and tables thereon, which is sturdy and permanent in nature. The tables and formula are laminated to the top of the desk under plastic material, so that they are not easily marred or obliterated by use, which is convenient to use, and arranged so as to provide a work desk for the student or other person using same, and storage shelves for models, books, or papers are provided therein. It may be used as a study desk, a drawing table, or as an aid in interpolating between mathematical tabular values. The top can be used also as a convenient reference source for standard mathematical formulas.

Other and further objects of the invention will become apparent upon reading the detailed specification hereinafter following, and by referring to the drawings annexed hereto.

A suitable embodiment of the invention is shown in the attached drawing, wherein:

FIGURE I is a front perspective view of the interpolator and desk combination;

FIGURE II is a top plan View of the interpolator arm and T-head as it would appear when positioned on the top of the table;

FIGURE III is an enlarged cross-sectional, elevational view taken on the line III-III of FIG. Il;

FIGURE IV is a cross-sectional, elevational view taken on the line IV-IV of FIG. Il;

FIGURE V is an enlarged fragmentary top plan view of a portion of the top of the desk showing a section of a common logarithm form arranged thereon, with a segment of the interpolator arm positioned thereover, and showing the transparent cursor positioned to bracket two adjacent vertical columns of figures in the common logarithm table; and

FIGURE IV is a fragmentary, top plan view of a portion of the top of the desk showing a section of a logarithm of natural trigonometric functions table, with the transparent arm positioned thereover, bracketing two vertical rows of numerals in such form, and showing the transparent cursor, bracketing the vertical column of figures in which interpolation is to be made.

Numeral references are employed-to designate the various parts shown in the drawing, and like numerals indicate like parts throughout the various figures of the drawing.

The numeral 1 indicates the top of the desk which slopes downwardly and forwardly to provide a convenient work surface for the student or other person using the desk while seated in front thereof, and assuring that the top of the desk is clearly visible while seated thereat.

The top 1 is preferably supported on legs 2, which are braced by the frame members 3. Preferably the legs 2 and the frame membersk 3 are made of tubular steel construction which are plated with chrome or other polished and non-corroding plating material, or with durable baked enamel, to provide a relatively lightweight frame which is ornamental in appearance, and which will be maintained in such condition for a long period of time.

A table of common logarithm forms 4 are provided on the top of the desk 1 at the upper left corner thereof, and a table of natural trigonometric functions 5 is provided on the upper right hand corner ofthe top of the desk 1, so that such tables 4 and 5 are in transverse alignment, and the numerals thereon are in transverse alignment for the purpose hereinafter mentioned.

At the center of the top of the desk 1 is a logarithm 3 of trigonometric functions forms 6, which extends entirely across the middle of the desk top. At the lower left hand corner of the desk top, and extending transversely thereacross, is a table of proportional parts 7.

An arm S, made of transparent plastic material, extends entirely across the top of the desk 1, said arm having spacer lugs 8a formed on the bottom side thereof, to space same from the top of the desk for the purpose hereinafter mentioned.

A T-head 9 is pivotally attached to the outer end of the arm 8, said T-head having a strip of magnetic material 10 secured to the inner face thereof, said material being preferably made of polystyrene plastic material impregnated with metallic filings and magnetized. The magnetic material 1i) is preferably attached to the inner face of the ''-head 9 by adhesive or the head could be made of magnetized material. The head 9 is pivotally attached to the outer end of the arm 8 by means of a pivot bolt 11. rfhe T-head 9 has an arcuate slot 12 formed therein, and a knurled nut and bolt combination 13 extends through the outer end of the arm 8 and through the slot 12. The horizontal position of the arm S may be adjusted with relation to the top of the desk 1 by arcuately rotating same on the pivot 11, as the bolt 13 slides in the arcuate slot 12. In this manner the arm S may be perfectly aligned with the horizontal lines of figures on the mathematical tables on top of the desk 1, and after alignment may be fixed in such position by tightening down the knurled nut of 13.

A magnetically attracting metallic rim 14 of iron or steel alloy, is provided about the table top 1 to attract the magnetic material 10 thereto, so that the T-head 9 may be slid along the edge of the table, but is retained thereto in any adjusted position by the attraction of the magnetic material 10 to the metallic rim 14. Without the magnetic head, the arm 8 would slide down the sloping surface of the table top.

A pair of spaced parallel horizontal lines 15 are provided on the arm 8 for bracketing numerals on the mathematical forms in the manner hereinafter described.

A slidable cursor 16, made of transparent material, is slidably positioned on the arm 8, said cursor having overlapping flanges 16a thereon embracing the edges of the arm 8. The cursor 16 is slidable longitudinally on the arm 8, but preferably has a slight frictional engagement therewith so that it can be stopped and maintained at any adjusted position thereon. The lugs 8a on the bottom of the arm 8 space the arm from the desk top so that the cursor may be easily slid along the arm 8.

The cursor 16 has spaced parallel, vertical lines 17 thereon, for bracketing columns of tabular values in the manner hereinafter described.

The table top 1 preferably consists of a baseboard 18 made of pressed or laminated wood or fibrous material, to which is laminated a layer of plastic material 19 by heat and pressure in a well-known method. The mathematical forms, which are printed on paper 20, are then laid over the laminated table top 18 and 19, and an upper layer of plastic material Z1 is laid thereover and laminated thereto by heat and pressure, so that when such process is completed, the printed figures and formulas on the paper appear to be actually embedded in the plastic material overlaying the top of the desk. This provides a very attractive, as Well as durable, top for the desk in which the mathematical values and formulas are not easily marred or obliterated by use. The top of the desk so formed also provides a very smooth surface for a work desk or drawing table, thereby providing a multiple use for the desk, to wit, a work or drawing desk, and an aid in interpolation between mathematical values and a reference source for mathematical formulas.

At one side of the desk there is provided a level work surface 22 which is also preferably overlaid with plastic material, as described, and .underneath the surface 22 is provided convenient shelves 23 for storage of papers, models and books.

Other mathematical formulas, tabular values and symbols used in mathematics, may be laminated under plastic as hereinbefore described, on surface Z2.

The operation and function of the hereinbefore described desk and interpolator are as follows:

rl`he transparent arm 8 is placed in slidable position on top of the desk 1 with the magnetic strip 10 slidably engaged with the metallic rim 14 so that the head 9 is attracted to, and slidably attached to, the metallic rim 14. In such position the arm 8 is in transverse alignment with the transverse rows of numerals on the tables 4, 5 and 6. In the event that the horizontal lines 15 on the arm 8 are not in exact alignment with the transverse rows of numerals on the top of the desk, same may be adjusted into alignment therewith by loosening the knurled nut 13 and pivoting the arm 8 about the pivot 11 until the lines 1S are brought into alignment with the transverse rows of numerals, and the knurled nut 13 may again be tightened down to fix the arm S to the head 9 in such adjusted relationship.

Since in the common logarithm table 4 and natural functions table 5, interpolation must be made between transversely adjacent numerals, the lines 15 are so spaced apart with relation to the numerals on such forms that they will bracket only a single row of numerals, as shown in FIG. V.

On the other hand in the logarithms of trigonometric functions table 6, interpolation must be made between vertically adjacent numerals so that spacing between the horizontal lines of numerals on such form is so related to the spacing between the lines 15 that said lines of numerals 15 will bracket two horizontal rows of numerals on such form, as shown in FIG. VI.

In interpolating between two adjacent transverse numerals in the common logarithm and natural functions tables, the arm 8 is slid along the surface of the table until the row in which the two adjacent numerals appear is bracketed as shown in FIG. V.

The cursor 16 is then slid longitudinally along the arm 8 until the vertical lines 17 thereon bracket the two adjacent vertical columns of numerals where interpolation is to be made, as shown in FIG. V. The magnetic head 9 is attracted to the metallic rim 14 so that the arm 8 is held in such position. The user may then carry out the process of interpolation between the two numerals, and the numerals are maintained in bracketed position while the users attention is so diverted, thereby quickly solving the problem on which he is working. He may glance back and forth between the bracketed numerals and the work sheet without fear of losing his place and committing an error by working with the wrong row or column of figures.

On the logarithm of trigonometric functions form 6, interpolation is carried out by sliding the arm 8 along the table to bracket two rows of numerals as shown in FIG. VI, and the cursor may be slid longitudinally on the arm S as shown in such figure, to bracket the correct vertical column of numerals. Thereby interpolation can be carried out between two adjacent vertically arranged numerals in the manner hereinbefore described without fear of introducing error into the calculations by working with the wrong row or column of figures.

The device hereinbefore described is, of course, not conlined to interpolation between figures on mathematical tables, as described, but it can be employed to bracket rows and columns of numerals, or rows and columns of letters, symbols, or other indicia, on any type of columnated form in which it is desired to segregate a specic segment of something for ready reference.

It will be seen that I have provided a desk, drawing table, or the like, having mathematical or other forms laminated and permanently fixed to the upper surface thereof, which in conjunction with a transparent interpolator arm which is arcuately adjustable, and slidably and magnetically attached to the edge ofthe table, providing ease and convenience in bracketing rows and columns of numerals or other type of indicia, both laterally and vertically, on such desk where quick reference is required, and reducing the chance of error to a minimum.

It will be understood that other and further forms of the invention may be devised without departing from the spirit and scope of the appended claim.

Having described my invention, I claim:

ln a device of the class described, a desk; common logarithms and natural trigonometric functions arranged in columnated form across the top of the desk; logarithms of trigonometric functions arranged in columnated form on the top of the desk; a transparent arm slidably disposed on top of the desk; longitudinal parallel spaced lines on the arm, said lines being spaced apart to bracket a single row of horizontally aligned figures on the common logarithms and natural functions forms, and to bracket two rows of horizontally aligned gures on the logarithms of trigonometric functions form; a transparent cursor slidable longitudinally on the arm; means on the lower surface of the arm slidable on the upper surface of the desk to space the arm from such upper surface; vertically disposed spaced parallel lines on the cursor arranged to bracket vertical columns of figures on the forms; magnetic attracting material attached along the edge of the desk top; a head on one end of the arm having a surface thereon slidably engaging the edge of the desk top having the magnetic attracting material thereon; and magnetized material on the inner surface of the head arranged to be attracted to the magnetic attracting material on the edge of the desk.

References Cited in the tile of this patent UNITED STATES PATENTS 279,263 Martin June 12, 1883 357,663 Greenlee Feb. 15, 1887 421,512 Potter Feb. 18, 1890 456,553 Carr July 28, 1891 1,336,900 Galloway Apr. 13, 1920 1,713,025 Castleman May 14, 1929 2,257,005 Grosse Sept. 23, 1941 2,516,569 Harris July 25, 1950 2,568,575 Wickman Sept. 18, 1951 2,588,079 Boehm Mar. 4, 1952 2,801,797 Morgan Aug. 6, 1957 FOREIGN PATENTS 824,794 Great Britain Dec. 2, 1959 

